package com.my.chapter21;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class practice13 {
    private static final int SIZE = 10;
    private static CircularSet serials =
            new CircularSet(1000);
    private static ExecutorService exec =
            Executors.newCachedThreadPool();
    static class SerialChecker implements Runnable {
        public void run() {
            while(true) {
                int serial =
                        SerialNumberGenerator.nextSerialNumber();
                if(serials.contains(serial)) {
                    System.out.println("Duplicate: " + serial);
                    System.exit(0);
                }
                serials.add(serial);
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        for(int i = 0; i < SIZE; i++)
            exec.execute(new SerialChecker());
        TimeUnit.SECONDS.sleep(100);
        System.out.println("No duplicates detected");
        System.exit(0);
    }
}

class SerialNumberGenerator {
    private static int serialNumber;
    public synchronized static int nextSerialNumber() {
        return serialNumber++;
    }
}

class CircularSet{
    private int[] array;
    private int len;
    private int index = 0;
    public CircularSet(int size){
        array = new int[size];
        len = size;
        for(int i=0;i < size;i++){
            array[i] = -1;
        }
    }
    public synchronized void add(int i){
        array[index] = i;
        index = ++index % len;
    }
    public synchronized boolean contains(int val){
        for(int i=0;i < len;i++){
            if(array[i] == val)
                return true;
        }
        return false;
    }
}
